Juice diets have surged in popularity as "quick fix" programs, promising rapid weight loss, detoxification, improved skin, and enhanced mood. But do these diets deliver on their promises, and are they safe and sustainable? This article explores the science behind juice cleanses, examining their potential benefits and risks, and offering healthier, more sustainable alternatives.
What is a Juice Cleanse Diet?
Juice diets, also known as juice fasts or detoxes, involve consuming primarily or exclusively fruit and vegetable juices. Some juice diets require abstaining from all other foods, while others allow specific solid foods in addition to juices. Regardless of the approach, these diets typically involve a significant calorie restriction. The most extreme juice diets are usually followed for a short duration, ranging from three days to one week, while less restrictive versions may be extended for longer periods. Juice-only diets are generally vegetarian and often vegan, although some plans permit the addition of honey or yogurt.
How Does the Juice Diet Work?
The core principle of a juice diet revolves around consuming fruits and vegetables in their liquid form. These juices can be prepared at home or purchased pre-made. Strict juice cleanses eliminate solid foods entirely, while some variations may incorporate soups. Green juices, made from vegetables like celery, spinach, or kale, are frequently included to ensure adequate intake of leafy greens.
What Can You Eat on the Juice Diet?
As the name implies, a juice diet primarily consists of juiced fruits and vegetables. While homemade juices are an option, ready-made versions are also available. The strictest forms of the diet exclude all solid foods, although certain plans may permit soups.
During the juice-only phase, suitable ingredients include:
Read also: Explore the pros and cons of fruit juice detoxes.
- Apples
- Berries
- Bananas
- Citrus fruits
- Kiwi
- Pomegranate
- Pineapple
- Lemon juice
- Watermelon
- Bell peppers
- Cucumber
- Celery
- Fresh herbs
- Leafy greens (kale, spinach, chard)
- Cruciferous vegetables (broccoli, cauliflower, Brussels sprouts)
- Carrots
- Zucchini
Many 21-day juice fasts include a seven-day phase of consuming only freshly made fruit and vegetable juices and water. Some people dilute their juice with equal parts juice and filtered water, while others drink 8 ounces (oz) of juice followed by 8 oz of water. A second phase of "light" eating often involves three to seven days of eating low-calorie, plant-based foods like soups, salads, and smoothies. A third phase of "raw" eating may also be included, in which about 75 percent of your intake comes from fresh, raw foods. The other 25 percent can come from cooked foods. Meat and poultry are usually discouraged, as are cooking methods like frying and breading.
Foods to avoid typically include:
- Meats (chicken, pork, beef, lamb)
- Dairy foods (cheese, milk, yogurt)
- Beans and legumes
- Grains (bread, pasta, rice, oats, quinoa)
- Nuts and seeds
- Added fats (cooking oils, salad dressings, mayonnaise)
- Sugar-sweetened beverages
- Alcohol
Is the Juice Diet Healthy?
Juicing removes dietary fiber and other beneficial nutrients found in the skin and seeds of fruits and vegetables. For example, the white pith of citrus fruits, a source of protective flavonoids, is often discarded during juicing. Essential nutrients like iron, crucial for energy levels, and fats, including omega-3 fatty acids, are also likely to be deficient in a juice-only diet. Fats are vital for hormone production, cognitive function, and nutrient absorption. Protein, necessary for muscle maintenance, growth, repair, and hormone production, is another macronutrient often lacking in these diets.
The Sugar Content of Juices
Fruit juices are naturally high in sugar. Juicing releases sugars, converting them into "free" sugars, which are rapidly absorbed into the bloodstream. The absence of fiber exacerbates this effect, potentially leading to rapid blood sugar spikes, increased hunger, and cravings. Some experts are concerned that the consumption of fructose in liquid form may negatively impact the liver and interfere with the brain's satiety signals, potentially increasing appetite. The British Dental Association has also linked juice consumption to tooth decay.
Juicing for Weight Loss
Most individuals experience some weight loss on a juice diet due to the elimination of fats and proteins and the significant reduction in calorie intake. However, this weight loss is often unsustainable once regular eating habits resume. The amount of weight lost varies depending on individual circumstances, including initial weight.
Read also: Juice Cleanse: Benefits and Risks
Some evidence suggests that a short-term, three-day juice diet may benefit gut health, which could contribute to long-term weight management by influencing the balance of gut bacteria.
Juicing for Better Skin
Raw fruits and vegetables are rich in skin-supportive nutrients like vitamin C and beta-carotene (vitamin A). However, the absorption of fat-soluble vitamins (A, E, and K) may be compromised due to the lack of fat in a juice diet. Healthy skin also requires protein and polyunsaturated fats like omega-3 fatty acids, which are typically deficient in juice-only diets.
Improvements in skin condition associated with juice diets may also be attributed to the elimination of refined sugars, processed foods, and alcohol.
Mood-Boosting Effects
Improvements in mood reported during juice diets may be linked to the elimination of processed foods, junk foods, alcohol, caffeine, and refined sugars.
A Nutritionist's Perspective
Limited scientific evidence supports the use of juice diets for improved health. Following a juice diet for more than a few days may lead to nutrient deficiencies and associated health problems. While fruits and vegetables are essential for a balanced diet, unsweetened juice only counts as one of the recommended five daily servings, regardless of the quantity consumed, due to the lack of fiber.
Read also: Renal Diet Guide: Navigating Orange Juice Consumption
The body's natural detoxification system, comprising the liver, kidneys, lungs, gut, and skin, eliminates the need for juice diets to initiate detoxification.
If considering a short-term juice diet, homemade juices made with fresh, organic produce, focusing on vegetables and flavoring with a small amount of fruit, are recommended. Juicing only the necessary amount and adding back some of the extracted pulp can help optimize nutrient intake and fiber consumption. Varying the fruits and vegetables used can also enhance nutrient diversity.
Who Should Avoid Juice Diets?
Individuals with medical conditions or those taking prescribed medications should consult their doctor before making drastic dietary changes. The high sugar content of juices can cause fluctuations in blood sugar levels, making juice diets unsuitable for individuals with diabetes or blood sugar management issues.
Juice diets should also be avoided by:
- Pregnant or breastfeeding women
- Elderly individuals or those under 18
- Individuals recovering from surgery
- Individuals with kidney or liver conditions
- Individuals with epilepsy
- Individuals with anemia or low blood pressure
- Individuals with a history of eating disorders
Do Juice Diets Work?
While juicing may provide a temporary energy boost and some weight loss, extreme diets that eliminate multiple food groups should be approached with caution. These diets are generally unsustainable, and weight regain is likely upon returning to regular eating habits. Furthermore, the high sugar content may increase hunger and negatively impact liver health, sleep, and dental health.
Potential Benefits of the 21-Day Juice Fast Diet (and Why They May Not Last)
By consuming only juice for a week (and very light meals for two additional weeks), you’ll trim your calorie intake considerably. For this reason, weight loss is likely during a 21-day juice fast.
However, juice fasting isn’t a healthy or sustainable path to long-term weight loss. Fruit and vegetable juices have virtually no protein, and are very low in calories. While that can promote weight loss, it’s mainly because you’re losing water and muscle. When you resume your usual eating habits, you’re likely to regain weight lost during a short-term fast.
The claim that a three-week juice fast will “detox” your body also doesn’t hold water. There is no scientific evidence that a juice diet helps you detox.
Your kidneys and liver do that job 24/7, so the best way to remove toxins is to support these organs with a healthy, balanced diet high in whole fruits, vegetables, and other high-fiber foods, and low in salt and added sugars, especially in ultra-processed foods and alcohol.
As for the mental and spiritual clarity purported to come from fasting, more scientific evidence is needed. In a small study published in 2023, men who did a water-only fast for eight days experienced no changes to their mental well-being.
However, another - older - small study looked at 52 young women who fasted for 18 hours. The women reported a variety of emotional impacts, from elevated positive feelings of achievement, reward, pride, and control to increased irritability.
Risks Associated with Juice Cleanses
Unsustainable Weight Loss
Severe caloric restriction is not sustainable for most people and rarely leads to long-term weight loss. It may also increase a person’s risk of other complications. In most cases, a person will return to their starting weight quickly once caloric restriction ends.
Low Blood Sugar
Consuming an insufficient number of calories can cause a person to experience symptoms relating to low blood sugar, including fainting, weakness, dehydration, headaches, and hunger.
Malnutrition
A person on a juice cleanse may not consume enough proteins or fats. Both of these are crucial to physical health, healing, and brain function. Eliminating food groups for extended periods may also lead to malnourishment.
Dehydration
If a juice cleanse includes laxatives or other methods of bowel stimulation, a person could lose too many nutrients in their stool. This can lead to dehydration and imbalanced electrolytes.
Kidney Health Concerns
Some foods are high in oxalate, a compound that can increase a person’s risk of kidney problems when consumed in high quantities. Foods high in oxalate include spinach and beets. People living with chronic kidney disease may be at risk of oxalate nephropathy. In rare cases, healthy people may also be at risk of this. Oxalate nephropathy is a condition in which the body cannot excrete enough oxalate through urine, causing it to build up in kidney tissue. In rare cases, this can cause kidney failure.
Lack of Detoxification Evidence
Advocates of juice cleanses often claim that the programs can help remove toxins from a person’s system. An increase in fluid consumption can help kidney function, and some nutritional compounds may help in the removal of non-organic waste products in the body. However, there is insufficient evidence to suggest that juice cleanses or other detoxification diets impact the ability to remove toxins.
Nutrient Deficiencies
Though fruits and vegetables have lots of important nutrients, they’re notably lacking in protein, fat, and certain micronutrients like vitamin B12. Going without these nutrients for too long could lead to deficiencies.
Elevated Blood Sugar
Fruit juice is very high in sugar, which can cause high blood sugar in someone with diabetes or prediabetes.
Undesirable Changes from Low Fiber
Juice diets lacking in fiber caused harmful changes to oral and gut bacteria after just three days. Meanwhile, low fiber intake could slow down your digestion, causing constipation.
Social Isolation
The restrictive nature of a 21-day juice fast could mean three weeks of difficulty socializing over meals. During this time, you might lose out on the pleasure of enjoying food with others.
Alternatives to Juice Cleanses
Balanced Diet
Eating a balanced diet and staying adequately hydrated are the best ways to maintain a healthy weight and support the body’s removal of toxins.
Plant-Based Diets
Based on minimally processed foods, these diets are naturally rich in fruit and vegetables and are associated with reduced body weight. With good planning, a plant-based diet can provide all the nutrients necessary for good health.
Intermittent Fasting
This involves abstaining from eating for limited periods and eating a regular diet at other times. Reviews have linked intermittent fasting with weight loss and improvements in insulin sensitivity.
Smoothies
If you like the idea of drinking your fruits and vegetables, try making smoothies using kale or spinach mixed with berries, apples, bananas - whatever fruits you like. Unlike pressed juice, smoothies are made by blending ingredients, using whole fruits and vegetables. You can also add extra protein to your smoothie by including Greek yogurt or milk. You’ll get all of the nutrients of juicing the same ingredients, plus the benefits of fiber and more.